Plans for a large master-planned community in Casa Grande have hit a major roadblock: The state of Arizona says there might not be enough water underground in aquifers to support the new rooftops.

And the development isn't the only one with a water problem that could halt construction.

So far, according to the Arizona Department of Water Resources, 15 proposed projects in the Pinal County area have received letters from the state notifying them that groundwater necessary for their projects could be in short supply.

It's likely the first time the state has sent such letters, but state officials say there is no reason to panic.

Looking 100 years out

Aquifers under the Pinal County area aren’t drying up anytime soon, stateand local officials say. They say there is plenty of water underground to supply homeowners and that thousands of planned homes can still be built.

The problem, however, comes when the state looks long term — 100 years out, to be exact.

Under state law, developers cannot build subdivisions in some areas of the state unless they can prove they have an 100-year water supply.

State and county officials say the situation isn’t as dire as it might appear. They say much of the water is allocated for developments that exist only on paper — projects that were proposed during the housing craze and might never get built.

“It’s reserved for speculative projects,” says Doug Dunham, legislative liaison for the Department of Water Resources. “Right before the economic downtown there was a huge boom of applications in the Pinal (area).”

Dunham says the department is looking at whether it can free some tied-up water and tweak its groundwater flow modeling, which relies on conservative assumptions, to more accurately reflect available water. He says homeowners today use less water than in decades past.

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Water-policy experts arediscussing those issues in the Pinal County area as part of broad-based talks Gov. Doug Ducey has initiated to reshape water policy in Arizona.

Ducey’s administration has cast the talks as a chance to get ahead of the state’s water challenges. Pinal’s situation is a small piece of the policy discussion, but it illustrates one type of hurdle that other areas could eventually face.

Some water experts say the scenario should be a wake-up call for the Pinal area and other parts of the state where the heavy reliance on aquifer pumping is a challenge that won't go away.

Long-term groundwater scarcity?

David Snider, a former Pinal County supervisor and chair of the Pinal County Water Augmentation Authority, says the area has a “definite scarcity when it comes to supplies of renewable water.”

Snider says while he agrees there are likely short-term solutions, the long-term challenge remains.

“It is not just enough to rearrange the deck chairs on the Titanic,” he says.

He says Pinal must find new sources of renewable water, whether it’s negotiating with tribal communities that have excess Colorado River water or pursuing more creative options like desalination of ocean water.

“When you have a finite resource and you have a demand that continues and perhaps even grows, at some point, you can figure out what will happen,” Snider says.

Under state law, developers can only build subdivisions in areas with historically significant use of groundwater if they can prove they have a 100-year assured water supply.

These zones, also known as active-management areas, have special rules governing the use of groundwater to prevent depletion of the state’s finite aquifers.

In the Pinal Active Management Area, a roughly 4,000-square-mile zone that encompasses much of Pinal County, the state’s current modeling shows that demand for groundwater could exceed aquifer capacity if more development occursthan already is accounted for in the state's modeling.

That means developers who haven’t already received approval of their 100-year water supply, like Copper Mountain Ranch, might be unable to provide tap water for the homes they hope to build.

Other parts of the state governed by groundwater rules, such as Phoenix and Tucson, have more access to surface water from the Colorado River and other sources. The Pinal area, meanwhile, depends on groundwater to supply much of its new development.

‘Not a panic situation’

One of the first projects where the projected lack of available groundwater has become an issue is a huge master-planned community dubbed Copper Mountain Ranch.

Late last month, the Department of Water Resources sent the letter notifying the developer of the project’s first 151-home phase that the state's newest model shows a possible shortage of groundwater.

“(Modeling) results indicate that sufficient groundwater may not be physically available to serve Copper Mountain’s estimated water demand when considered with other existing uses and approved demands in the area,” the state wrote.

At full build-out, Copper Mountain Ranch is slated to have 12,466 homes, hundreds of apartments, an 18-hole golf course and shopping centers.

Jordan Rose, a land-use attorney who represents Copper Mountain Ranch, is a member of the governor’s water-discussion group. She says the situation in Pinal is no cause for concern and has an easy resolution.

“There’s plenty of water in Pinal County for decades to come,” Rose says. “This is not a panic situation. This is merely an update to the modeling.”

But others described the situation as a more serious challenge for the Pinal area, one that requires significant investment in renewable water supplies.

Pinal County Supervisor Stephen Miller, who represents Casa Grande, also is part of the governor’s talks. He, too, is hopeful the state can resolve the issue but says a fix should have come before developers found themselves in limbo.

“On (the state’s) ledger, there’s not enough water for future development,” Miller says. “Hindsight is 20/20. We should have probably been talking about this three years ago.”

And experts say what's happening in Pinal could be a warning for the rest of the state.

Kathleen Ferris, a senior research fellow at the Kyl Center for Water Policy at Arizona State University, says challenges in the Pinal active management area could happen in other areas that become too dependent on groundwater.

She says the area must ultimately find ways to get a more renewable supply of water, such as surface water from the Colorado River, to support sustainable residential growth.

“It has to be addressed with a clear vision for fixing the problems rather than just pretending that we’ve fixed them," Ferris says. "That means that the growth that occurs is growth that you can sustain."